1. Field of the Invention
The present invention relates generally to a socalled picture-in-picture type television receiver in which a sub-picture screen is inset into a main picture screen in a picture-in-picture fashion.
2. Description of the Prior Art
In the prior art, there is known a television receiver of a so-called picture-in-picture type in which a sub-picture is displayed on a sub-picture screen within a main picture screen in an inset fashion.
As will be described later, this picture-in-picture type television receiver includes a memory to reproduce a sub-picture on the sub-picture screen. By controlling the writing in and reading out of the memory, this television receiver is capable of reproducing a picture on the sub-picture screen as a real moving picture or still picture.
This picture-in-picture television receiver also has separate circuits for generating a main picture signal and a sub-picture signal so that the cathode ray tube can independently display on the main and sub-picture screens pictures based on the video signals from different video signal sources. The pictures displayed on the sub-picture screen can be real moving pictures or still pictures which are the same as or different from the picture being displayed on the main picture screen.
The viewer controls what is to be displayed by means of an operation key, however, it is inconvenient, confusing to the viewer, and expensive to provide separate operation keys for each of the separate circuits for generating the main and sub-picture signals.
Further, the television receiver and its remote controller each have only a limited space in which operation keys used for various control operations can be mounted. There is then a problem that it is difficult to increase the number of the operation keys.